title: Tensile bond characteristics between composite resin and resin-modified glass-ionomer restoratives used in the open-sandwich technique.
abstract: BACKGROUND
  The clinical success of large class II resin-modified glass-ionomer cement/composite resin (RMGIC/CR) 'open-sandwich' restorations in permanent or primary molars may be influenced by certain bonding parameters.
  
  
  OBJECTIVE
  To examine in vitro the effect of placing/curing mode on the RMGIC/CR bond strength.
  
  
  METHODS
  Two restoratives, a CR (Z250), a RMGIC (Vitremer) and a bonding agent (Adper Single Bond 2), all of 3M ESPE, were used for preparing five groups of seven specimen sticks each. The bond between the two restorative materials at the stick centre was created in the three test groups by: (A) 1-step placing RMGIC in contact with CR, then photocuring; (B) 2-step RMGIC placing/curing, then CR placement/curing; (C) 3-step RMGIC placing/curing, bonding agent placing/curing, CR placing/curing. Control groups consisted of sticks made of CR alone (D, positive) and RMGIC alone (E, negative). The specimens were subjected to tensile stress measurements in an Instron dynamometer and examined by scanning electron microscope for type of failure.
  
  
  METHODS
  Tensile bond strength, tensile strain and elastic modulus differences were examined with one-way ANOVA and Tukey test.
  
  
  RESULTS
  Among experimental groups, Group C exhibited significantly higher tensile strength (MPa) means (A = 12.11 ± 4.72, B = 15.69 ± 5.18, C = 19.08 ± 4.05) and significantly higher tensile strain (%) means (A = 0.50 ± 0.11, B = 0.64 ± 0.19, C = 0.98 ± 0.24), compared to Group A, at p = 0.05. Group D had significantly higher tensile strength and strain than all other groups. No statistically significant differences were observed in the elastic modulus. The use of bonding agent (Group C) resulted in absence of adhesive failures as seen by SEM.
  
  
  CONCLUSIONS
  The use of bonding agent improved the CR/RMGIC bond by tensile strength and strain tests.
authors.affiliation: Department of Paediatric Dentistry, Dental Faculty, Aristotle University of Thessaloniki, University Campus, 54124, Thessaloniki, Greece, sfragkou@hotmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Fragkou
authors.forename: A
authors.initials: A
authors.lastname: Nikolaidis
authors.forename: D
authors.initials: D
authors.lastname: Tsiantou
authors.forename: D
authors.initials: D
authors.lastname: Achilias
authors.forename: N
authors.initials: N
authors.lastname: Kotsanos
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D019279:Resin Cements / Q000737:chemistry; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D005899:Glass Ionomer Cements; D019279:Resin Cements